Disk drives are digital data storage devices which can enable users of computer systems to store and retrieve large amounts of data in a fast and efficient manner. A typical disk drive includes a plurality of magnetic recording disks which are mounted to a rotatable hub of a spindle motor and rotated at a high speed. An array of read/write transducers is disposed adjacent surfaces of the disks to transfer data between the disks and a host computer. The transducers can be radially positioned over the disks by a rotary actuator and a closed loop, digital servo system, and are can fly proximate the surfaces of the disks upon air bearings.
A plurality of nominally concentric tracks can be defined on each disk surface. A preamp and driver circuit generates write currents that are used by the transducer to selectively magnetize the tracks during a data write operation and amplifies read signals detected by the transducer from the selective magnetization of the tracks during a data read operation. A read/write channel and interface circuit are connected to the preamp and driver circuit to transfer the data between the disks and the host computer.
The servo system can operate in two primary modes: seeking and track following. During a seek, a selected transducer is moved from an initial track to a destination track on the corresponding disk surface. The servo system applies current to an actuator coil to first accelerate and then decelerate the transducer toward the destination track.
During the seek, the servo system may sequentially measure the actual velocity of the transducer and adjust the current in relation to velocity error (i.e., the difference between the actual velocity and a target velocity). As the transducer approaches the destination track, the servo system initiates a settle mode to bring the transducer to rest over the destination track within a selected settle threshold, such as a percentage of the track width from track center. Thereafter, the servo system enters the track following mode wherein the transducer is nominally maintained over the center of the destination track until another seek is performed.
As will be appreciated, a disk drive is primarily utilized to transfer data between the tracks of the disks and the host computer. Such data transfer operations usually cannot occur during a seek, but rather require the drive to be in track following mode. Hence, to maximize disk drive data transfer rate capabilities, disk drives can attempt to obtain minimum average seek times. However, the forces that can be exerted on the actuator to obtain minimum average seek times can cause vibration of the actuator and the disk drive, and can result in a decrease in the seek performance and undesirable acoustical noise.
In addition to the vibration that may result from forces that may be exerted on the actuator to obtain minimum seek times, the electric current that may be required to be applied to the actuator coil motor of a disk drive in order to obtain minimum seek times may result in undesirable heating of the disk drive assembly and/or elements thereof. Heating of the disk drive assembly may have a number of deleterious effects on the operation of a disk drive. For example, since various components of a disk drive may have different coefficients of thermal expansion, heating of the disk drive, or components thereof, may result in mechanical instability within the disk drive, which may result in errors in drive operation. Further, excessive heat may damage sensitive components of a disk drive, such as the platter surfaces, the printed circuit board assembly (PCBA) and associated components, the read/write transducer, the pre-amplifier circuit and/or other components.
Conventional disk drives include circuitry configured to shut the disk drive down if a temperature associated with the disk drive exceeds a predetermined threshold. A temperature associated with the disk drive may include, for example, the temperature within the case of the disk drive, the ambient temperature of the environment in which the disk drive is operated, a temperature sensed at the PCBA, and/or the temperature of a component of the disk drive. When the temperature of the disk drive exceeds the threshold temperature, the result may be an abrupt shutdown of the disk drive, which may result in loss and/or corruption of data.
One approach to thermal management in disk drives is disclosed in U.S. Patent Application Publication No. 2004/0264036 to Ding et al. Ding et al. disclose a method of determining a seek profile compensation value that can be used to compensate a pre-defined seek profile for temperature. Seek profile compensation values are determined for a plurality of device operating temperatures and/or for a plurality of device operating temperatures and seek lengths, and are used during disk drive operation to compensate seek profiles based on the device operating temperature and/or seek length at the time a seek is executed.